1. Technical Field of the Invention
This invention relates to cellular telecommunications networks and, more particularly, to a cellular telecommunications network utilizing United States cellular standards and providing seamless interoperability between exchanges operating in both 800-MHz and 1900-MHz hyperbands.
2. Description of Related Art
North American cellular telecommunications networks have traditionally operated in two frequency bands (A and B) in the 800-MHz hyperband. The most recent evolution in cellular telecommunications involves the adoption of six additional frequency bands (A-F) in the 1900-MHz hyperband for use in handling mobile and personal communications. The 1900-MHz hyperband is also known as the Personal Communication Services (PCS) hyperband. Frequency bands within the 800-MHz hyperband and the 1900-MHz hyperband are defined in EIA/TIA Standard IS-136 and the PN3388-1 and PN3388-2 Specifications, which are hereby incorporated by reference herein. Other standards which define cellular telephone operations in North America include EIA-627, EIA-553, and the intersystem signaling standard IS-41 which are also incorporated by reference herein.
Each of the frequency bands specified for the cellular and PCS hyperbands is allocated a plurality of voice or speech channels and at least one access or control channel. The control channel is used to control or supervise the operation of mobile stations by means of information transmitted to and received from the mobile stations. Such information may include, but is not limited to, incoming call signals, outgoing call signals, page signals, page response signals, location registration signals, voice channel assignments, maintenance instructions, short message service (SMS) messages, and cell selection or reselection instructions as mobile stations travel out of the radio coverage of one cell and into the radio coverage of another cell. The voice channel is used to carry subscriber telephonic communications as well as messages requesting mobile station assistance in making hand-off evaluations. The control and voice channels may operate in either an analog mode or a digital mode.
Existing cellular telephone networks may simultaneously support radio telecommunications on multiple frequency bands. For example, a mobile switching center (MSC) may control transmission and reception equipment at a base station to operate one cell in the 800-MHz hyperband and another cell in the 1900-MHz hyperband. In addition, adjacent exchanges, controlled by different MSCs, may have cells that operate in the 800-MHz hyperband or cells that operate in both the 800-MHz and 1900-MHz hyperbands. Thus, as a mobile station roams throughout the coverage area of a single MSC, or from one MSC to another, the mobile station may pass to and from any combination of cells operating in the 800-MHz hyperband and dual-hyperband capable cells operating at both 800 MHz and 1900 MHz. As more frequency hyperbands come into use, roaming mobile stations will roam through an increasingly complex map of available hyperbands.
As a mobile station roams out of the coverage area of a cell, measurements of signal strengths of neighboring cells must be taken to assess whether the mobile station should reselect a particular neighboring cell for service (when in the idle mode) or be handed off to the neighboring cell (when in the busy mode). Existing cellular telecommunications networks, however, are not capable of performing the functions necessary to provide seamless interoperability between cells operating in different hyperbands and in different MSCs.
Telephone calls involving asynchronous data and facsimile (fax) services impose additional requirements on the telecommunication network. In order to establish and maintain a robust connection acceptable for the transmission of data and fax services between exchanges, an enhanced intersystem signaling protocol is required to communicate a set of commands between MSCs. This enhanced intersystem signaling protocol is distinctly different from the protocol necessary for voice transmission, and must provide a terminating MSC with information necessary in call delivery and/or handoff of voice, data or fax calls. In addition, intersystem signaling messages must provide information and verification on whether a particular subscriber has authorization to use the data and fax services.
Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, a prior art reference exists that discusses subject matter that bears some relation to matters discussed herein. One such prior art reference is U.S. Pat. No. 5,446,553 to Grube. This reference is discussed briefly below.
Grube relates to a wireless fax reception method with roaming. Specifically, the patent provides for a communication device, which roams within a communication system, the ability of maintaining contact with other communication units, even while the unit is away from its home sub-system. The communication system comprises a wide area paging system which includes a wide area paging controller (WAPC) which controls at least one local area paging controller. When the communication unit is away from its home system, the home system sends out a page via the wide area paging system in order to locate the communication unit and directs the unit to a local sub-system which the unit can use to communicate with the calling unit. However, Grube does not teach or suggest a wireless phone system since there are no call delivery principles underlying the invention. Additionally, the roaming described in this patent is not at the level necessary for use by a mobile phone system.
It would be a distinct advantage to have a cellular telecommunications network capable of controlling overlapping or adjacent cells operating in multiple hyperbands and in different MSCs in such a way that mobile stations capable of operating in multiple hyperbands may operate seamlessly between such cells for voice, data and fax services. It is an object of the present invention to provide such a cellular telecommunications network.